This invention relates generally to control devices and in particular to a thermostat, a method of operating a thermostat, an electrical circuit, and a method of heating a temperature sensing means of a thermostat.
In the past, various types of thermostats were utilized for controlling the operations of a heating system and a cooling system associated with a given space so as to regulate the temperature of the space. One of the past thermostats was of the dual or automatic type having a pair of temperature sensing devices for generally controlling the operations of the heating system and the cooling system, respectively, and such temperature sensing devices were respectively actuated by a pair of temperature setting indicators which were manually movable to select a desired temperature for the space. For instance, if heat was desired in the space, the heating temperature setting indicator was manually moved to the selected desired temperature setting for the space, and the temperature sensing device associated with the heating temperature setting indicator was actuated to a position in which the energization of the heating system was controlled so as to thermostatically regulate the temperature of space. Of course, in response to the temperature setting manual movement of the heating temperature setting indicator, the cooling temperature setting indicator and the cooling temperature sensing device associated therewith were driven to a position in which the cooling temperature sensing device was essentially incapacitated so that it could not effect actuation of the cooling system in response to the temperature of the space sensed by the cooling temperature sensing device. While these dual thermostats may have many salient features, it is believed that a disadvantageous or undesirable features thereof may reside in the adverse economics of providing a pair of temperature sensing devices and temperature setting indicators for respectively controlling the operation of the heating system and the cooling system.
Also in the past, thermostats of the manual type were also provided to control the heating system and the cooling system. In the past manual thermostats, means was provided to enable either the heating system or the cooling system, and a single temperature sensing device was associated with a temperature setting indicator which was manually moved to select the desired temperature of the given space. Of course, the aforementioned single temperature sensing device was responsive to the temperature in the space to control the energization of the enabled one of the heating system and the cooling system. Many of the past manual thermostats were provided with a universal anticipation heater for the temperature sensing device thereof, and it is believed that one of the disadvantageous or undesirable features of such universal anticipation heating schemes was that the cycle rate was lower in the cooling mode operation of such past manual thermostats having a universal anticipation heater than in the heating mode operation thereof by a fixed ratio. Of course, since the cycle rate affects the life of valuable system components, such as a heat pump compressor for instance, it is desirable to have as high a cycle rate that will provide adequate comfort and yet as low a cycle rate that will maximize the life of the component. Furthermore, another disadvantageous or undesirable feature of the past manual thermostats is believed to be that the control point or temperatures of the space would gradually rise as the demand for heat or duty cycle was required and then the space temperature would drop upon the transition of the such past thermostat from the heat mode to the cool mode by operation of its heat or cool system selection switch.